Hepatitis B (HBV) is a serious viral disease that can result in acute massive hepatic necrosis, chronic active hepatitis, and cirrhosis of the liver. HBV vaccines are commercially available and HBV vaccination is now recommended for all infants, adolescents, health workers and others who may be exposed to the virus through their work. Three HBV vaccine injections are required to generate protective immunity. Compliance depends on completing three visits to the healthcare provider. Incomplete vaccination is common and often attributed to scheduling difficulties. The vaccination success rate could be improved if only one dose were needed for full protection. There have been many attempts to address the need for single dose formulations for vaccines. Kitchell and Crooker (1997) studied the physico-chemical properties of alum, the adjuvant used in the approved HBV vaccine, and they made an important observation about the hydration behavior of this material. Their discovery led to a simple and elegant method of formulating alum-adjuvanted hepatitis A vaccine as a single-dose injection giving multiple delayed pulses. This innovative approach to reformulation is also appropriate for the HBV vaccine. BIOTEK believes that it has gained further insight into the techniques needed to prepare a single dose HBV vaccine which provides three discrete pulses of vaccine exposure. The formulation will utilize the established HBV vaccine antigen and adjuvant, and a FDA approved biodegradable polymeric excipient. The specific aims of the Phase I project are to prepare and test in vivo both one month and four month delayed pulse formulations. PROPOSED COMMERCIAL APPLICATIONS: The technology, first directed at an improved hepatitis B vaccine formulation, could be transferred to hepatitis A vaccine and to the childhood DPT vaccination series. One important application in the future may be with an AIDS vaccine, where relaible single-dose protection for high risk populations may be especially important.